For a period of time from the 1970s, plastic grocery bags have been replacing paper bags in the United States for the grocery, fast food and retail products industries because of various inherent advantages in plastic bags. For the most part, these plastic bags have been of the T-shirt type which include front and rear walls integrally joined at their sides and secured together at their bottoms and which define an open mouth portion at the top of the walls. Laterally-spaced handles extend upwardly from opposed sides of the bag at the open mouth portion in the top of the bag to provide ease in carrying of the bag by the consumer. A detaching central tab is provided at the top of each of the walls in the open mouth portion. The handles and the central tab include apertures therein for mounting of the handles and the central tab on a rack which includes two outwardly-extending support arms laterally spaced from each other and a central tab retaining device at the top of a rack frame.
This type of bag/rack system was pioneered as the highly commercially successful QUIKMATE.RTM. bagging system and is disclosed in U.S. Pat. No. 4,676,378, now Reissue Patent Re. 33,264, which is assigned to the assignee of the present invention. This system allows a pack of bags constructed as described above to be supported on the rack and to be consecutively opened up one-at-a-time on the rack for loading of groceries or other food or retail products and then removed from the rack and from the bag pack.
An improvement to this bagging system relating to self-opening of the bags in the bag pack one-at-a-time on the bag rack as a loaded bag is removed from the rack was developed by the assignee of the present invention and is disclosed in U.S. Pat. No. 5,335,788. This improvement involves constructing the bags of at least 50 wt. percent high density polyethylene plastic material, corona treating at least an upper portion of the outer surface of the front and rear walls of each of the bags and providing at least one localized compressed area extending transversely through the bag pack in the upper portion of the bags such that the bag pack has a decreased thickness in the compressed area for releasably adhering adjacent corona treated outside wall surfaces defined by the localized compressed area and leaving adjacent inside wall surfaces defined by the localized compressed area unadhered to each other. Further details of this improved bag construction may be seen in the '788 U.S. patent which is incorporated herein by reference.
While the QUIKMATE.RTM. bagging system utilizing the inventions of the above two identified patents of the assignee of the present invention has been highly successful and has become the standard in the industry, there have been some attempts to further improve the system by making it easier to open each consecutive bag on the rack. There has also been a desire to avoid leaving any residue of the bag packs on the rack, such as having the detaching mounting tab detach from the rack rather than detach from the bag.
U.S. Pat. Nos. 5,074,674; 5,188,235; 5,269,605; 5,346,310 and 5,465,846 are directed to such attempted improvements to the QUIKMATE.RTM. bagging system to provide for ease in opening of each consecutive bag on the rack and/or to provide for a detaching central mounting tab which will detach from the rack and leave no residue on the rack. These patents disclose various concepts relating to rendering of the tab on the front wall of the bag "front-side-free" wherein the front wall of the bag and the mounting tab thereon will simply detach from the tab retaining device of the rack without tearing of the tab. These patents also disclose various configurations of mounting apertures in the central mounting tabs on both the back wall and the front wall of the bags which may include a cut slit or weakening tear line which facilitates tearing of the tab to detach the tab from the rack and leave no residue on the rack.
However, all of these so-called improvements to the QUIKMATE.RTM. bagging system to provide these two described advantages have additionally created other problems. These other problems include the lack of sufficient strength in the central mounting tab on the rear wall of the bag to prevent such central tab from prematurely tearing and detaching from the tab mounting device on the rack during opening up of the bag and prior to loading of the bag on the rack. The configurations and structure of the mounting apertures on the bag central mounting tabs also created problems in wedging and, therefore, leaving residue behind a conventional "D-ring" type tab mounting device on the rack which consists of an inverted U-shaped wire loop member extending outwardly from cross frame members on the rack. These problems also exist for plastic bags without handles and having only a central mounting tab extending upwardly from an open mouth of a bag for mounting the bag pack on a suitable rack.